Automated track-guided material handling system with electrical pulse programming

ABSTRACT

An automated material handling system utilizing a track-guided electrically powered material transporter and a plurality of work stations located in spaced relationship along the track. A common control circuit interconnects all the stations and is activated by an electrical pulse circuit operable from any station for selectively directing movement of the transporter to or from one of the stations along any portion of the track. The system includes safeguard control means for correcting or preventing ineffectual or overlapping programming of the transporter movement.

United States Patent 91 Beer [76] Inventor: Egon Beer, 1163 East 332ndStreet,

Eastlake, Ohio 44094 [22] Filed: Apr. 15, 1971 [21] Appl.No.: 134,136

[52] US. Cl ..104/88 [51] Int. Cl. ..B61l 27/04 [58] Field of Search...104/88; 187/29 R; 2l4/l6.4 B

[ Mar. 27, 1973 Primary Examiner-Robert G. Sheridan AssistantExaminer-George H. Libman Attorney-Isler & Omstein [57] ABSTRACT Anautomated material handling system utilizing a track-guided electricallypowered material transporter and a plurality of work stations located inspaced relationship along the track. A common control circuitinterconnects all the stations and is activated by an electrical pulsecircuit operable from any station for selectively directing movement ofthe transporter to or from one of the stations along any portion of the[56} References Cited track. The system includes safeguard control meansUNITED STATES PATENTS for correcting or preventing ineffectual oroverlapping programming of the transporter movement. 2,529,804 ll/l950Hamischfeger et al. ..lO4/88 2,707,666 5/1955 Becker ..2l4/l6.l EB 11Claims, 3 Drawing Figures m, \Zz Lin? Zl 2D 2 O 24 2 7 z \e u H 'e zs 38A 5 we 2 J j ()5 b A 4 PATENTEnmamra SHEET 1 OF 3 INVENTOR. BY EGONBEER.

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SHEET 3 OF 3 INVENTOR. EGoN BEER waxw- Wu AUTOMATED TRACK-GUIDEDMATERIAL HANDLING SYSTEM WITH ELECTRICAL PUISE PROGRAMMING BACKGROUND OFTHE INVENTION Automated material transporting systems are known to theart and in their most common form consist of implaced conveyorapparatus, such as roller conveyors or endless belt conveyors, by meansof which material loaded at or discharged from one work station iscontinuously transported to a specific, predetermined destination ornext work station. Another form of material handling system which is incommon usage is the continuously moving transport system using overheadmoving work carriers or the like which maintain constant motion in afixed, endless path of movement through work stations at which thematerial can be processed while in movement or can be unloaded from thecarrier, processed and loaded back onto the carrier for movement to thenext station.

There are other variations of these basic types of au tomated materialhandling systems, but all are directed primarily to continuous movementof the material conveying mechanism in a predetermined fixed pathbetween a plurality of work stations. There is an existing need in manymaterial handling situations for a flexible, selective system which isnot limited to an in-line or fixed path of movement of a continuousnature. Although it is possible to provide such a flexible materialhandling system with sophisticated electronic. circuitry and even withhigh frequency radio wave control or the like, the complexity and costof such electronic systems, as well as their operative maintenance,would preclude their use in many situations where a less costly butsufiiciently flexible and versatile electrical system of control couldadequately serve the purpose. The invention herein described is directedtoward this latter objective.

SUMMARY OF THE INVENTION An electrically driven, track-guided materialcarrier or transporter is mounted on an overhead rail orthe Any stationcan call the transporter from any other station or can send thetransporter to any other station by means of an electrical pulseselection system which initiates the movement of the transporter, setsthe necessary rail switches for the pathof movement that the transporteris to follow. to reach its station of destination, and stops thetransporter at the selected destination.

Six control lines andtwo power lines are common to all of the stationsin the system, thus permitting stations to be added, removed orrelocated by simply connecting them into the common circuit for allstations. The transporter unit has electrical connection with thecontrol circuitry through a single control line represented by a bus barmounted parallel'tothe track andengaging gliding collector shoes on thetransporter unit.

Each of the stations is provided with like electrical components whichprovide each station with its own actuating circuitry which is energizedin response to the electrical pulse selection which is made.Energization of a selected station precludes energization of any of theother stations on the common circuit.

A responding circuit is provided to serve allstations and selectivelyprovide energization for the initiation of movement of the transporterand the energization of the station of destination. Physically, theresponding circuit can be permanently installed in any desired locationwhere it can be electrically connected by a single line to thepreviously described transporter bus bar.

The transporter itself need not carry any components of the controlcircuitry for either the station circuits or the responding circuit andis equipped with a limit switch and a trip arm, neither of which iselectrically connected directly to the station circuits or theresponding circuit, but which will physically cooperate with circuitcomponents of any one of the station circuits which has been selectivelyenergized. Thereby, regardless of the number of stations which areemployed in the system, there is no need for any compensating changeinthe cooperating limit switch and trip arm of the transporter unit nor isany additional circuitry required for the transporter unit by reason ofthe addition or removal or relocation of any stations.

By this arrangement, a flexible and versatile material transfer systemis provided which is low in initial cost, does not require highlyskilled technicians forinstallation or maintenance, and provides forexpansion and change inthe, number and location of stations without anysignificant change in the common circuitry which is utilized.

Other objects and advantages of the invention will appear more fullyhereinafter.

BRIEF DESCRIPTION OF THE DRAWING FIG. '1 is a schematic representationof a material handling system utilizing the features of my invention.

FIG. 2 is a circuit diagram showing the individual circuitsof aplurality of stations and the common circuit for-all of the stations.

FIG. 3 is a circuit diagram of the responding circuit for all of thestations and its connection to the transporter starting circuit.

, DESCRIPTION .OFTI-IE PREFERRED EMBODIMENTS FIG. 1 of the drawingsschematically illustrates an exemplary automated material handlingsystem with a electrically driven transporter unit 1 1 preferably of theoverheadtype moving upon-and guided by one or more tracks or rails12;The main rail or track section 12 isillustrated as being endless, butincludes a merging branch track 12a and another branchtrack 12bextending from the branch 12a to the main track. Thestation 16 is shownlocated adjacent to a portion of the main track 12, the station 38 islocated adjacent to a portion of the branch track 12a, and the station75 is shown located adjacent to a portion of the branch track 12b. Thestations represent locations or areas at which the material may beloaded or unloaded for any desired purpose whatsoever, includingtesting, processing, finishing, painting, packaging, shipping, receivingor storage. In the illustrated example, the transporter 11 is shown ashaving a single direction of travel on the track, as indicated by thearrow, but, as noted above, the invention does not preclude movement ofthe transporter in a two-way direction, such as when a nonendless trackis employed having terminals between which the transporter travels inone direction or the other.

At the entrance junction between the track 12a and the track 12, asuitable movable track switch 13 is provided for selectively directingthe path of movement of the transporter either onto the branch track 12aor to maintain it on the main track 12. At the entrance junction betweenthe branch tracks 12a and 12b, a suitable movable track switch 14 isprovided to selectively define a path of movement either along theremaining portion of the branch line 120 or along the branch line 12b.The movement of the track switch 13 is controlled by a limit switch 15disposed adjacent to the track 12 at a location ahead of the trackswitch 13 and a limit switch 17 located adjacent to the branch track 120between the locations of the track switches 13 and 14. The limit switch15 is operatively disposed in the path of movement of a trip arm 18carried by the transporter 11 and, when the limit switch 15 is in anenergized state, engagement by the trip arm 18 causes the limit switchto close a conventional operating circuit (not shown) to cause movementof the track switch to a position defining a path of travel from themain track 12 to the branch track 12a. After the transporter 1 1 hasmoved past this junction, its trip arm engages the return limit switch17, which is always in an energized state, and which by means ofconventional circuitry (not shown) causes the track switch 13 to berestored to its normal position where it defines a path of movement onthe main track 12 which by-passes the branch track 12a. Similarly, alimit switch 19 is provided adjacent the track 12a ahead of the trackswitch l4and a return limit switch 20 is located adjacent to the track12b beyond the track switch 14 to cause a sequence of movement of thetrack switch 14 which will either direct the transporter onto the track12b or by-pass the track 12b and maintain the transporter on the track12a.

The return limit switches 17 and 20 are ordinarily maintained in anenergized state regardless of the particular station toward which thetransporter is being directed. However, the energization of the limitswitches 15 and 19 is controlled and dependent upon the station circuitof the particular station of destination which has been selected for thetransporter. As indicated by the line 21, the limit switch 19 isconnected only to the control circuit of the station 75, but the limitswitch 15 is connected by lines 22 and 23 to both stations 38 and 75respectively, so that it can be energized by the control circuit ofeither of these stations.

Each of the stations is provided with a solenoid operated trip arm, suchas indicated at 24 at station 16. The transporter is provided with alimit switch 25 which is adapted to be engaged by the station trip armwhen such trip arm has been energized by the station circuit. As will bemore fully described hereinafter, this actuation of the transporterlimit switch 25 results in the stopping of the transporter at aparticular station, such as the station 16 if its trip arm 24 has beenenergized.

As indicated by the lines 26, 27 and 28, all of the stations have commonconnections to a common circuit, here indicated by the block 29, and toa responding circuit, here indicated by the block 30, this commonconnection consisting of a series of six control lines and two powerlines which will be described in greater detail hereinafter. The commoncircuit 29 and the responding circuit 30 are interconnected by the line31. Additionally, the responding circuit is connected by a line 32 to abus bar 33 which is mounted to extend substantially parallel to thetrack and which constitutes an extension of the line 32. Circuitcomponents, to be described, on the transporter unit 11 have electricalconnection to the bus bar by means of conventional glide collector shoesor the like (not shown) by means of which the transporter unit maintainscontact with the bus bar during its movement to any location on thetrack.

As thus described in broad outline, it will be seen that the materialhandling system includes a plurality of stations, each having its ownstation circuit; a track guided transporter unit which is electricallypowered to move toward any selected station; a common circuit and aresponding circuit interconnected with each other and with all of thestations for the purpose of establishing and controlling the path anddestination of movement of the transporter in the programmed pathselected for it at any one of the station circuits and a bus barelectrically interconnecting the transporter and the responding circuitto initiate movement of the transporter in the programmed manner. Theelectrical circuitry employed to effect this selection and programmingwill now be described in greater detail.

Referring more particularly to FIG. 2 of the drawings, there isillustrated the common circuit, essentially within the outline of theblock 29, and the respective station circuits within the outlines of theblocks 16, 38 and75. Each of the several station circuits is identicalto the others, so that a description of the station circuit 16 will berepresentative of the circuits for the stations 38 and as well as of anyother existing stations or of stations which might be added to thesystem. The common circuit 29 will remain the same without regard to thenumber and location of the stations used in the system. Physically, thecommon circuit components may be permanently located in any suitablelocation together with the components of the responding circuit.

The power lines, represented by the hot line 34 and the neutral orground line 35 are common to all of the circuits shown in FIG. 2 of thedrawings as well as to the responding circuit and transporter startingcircuit shown in FIG. 3 of the drawings and, inasmuch as such powerlines are ordinarily available throughout the area in which the materialhandling system is located, they need not be particularly identifiedwith any one of the circuits to the exclusion of the others. In additionto these described power lines, the common circuit 29 includes asatellite hot power line 36, a satellite neutral power line 37 and thevisual signal control lines 39 and 40. These four control lines arerepresented by the line 41 in FIG. 1 of the drawings. The remaining twocontrol lines are a multiple-pulse transmission line 42 and asingle-pulse transmission line 43 which interconnect the stationcircuits with the responding circuit 30 and are indicated by the line 44on FIG. 1 of the drawings. These pulses are initiated by an electricalpulsing dial selector mechanism 45, one of which is located in eachindividual station circuit for the purpose of programming the station ofdestination of the transporter 11.

The hot power line which serves to feed all of the individual stationcircuits is the satellite line 36 which is energized by connection tothe hot power line 34 through the normally closed contact 46 of commoncircuit relay 47 when the transporter is not in a programmed state andthe circuit components of the system have not yet been energized.Assuming that the transporter unit 11 has previously completed its cycleof operation by stopping at its station of destination number 75, itwill now be assumed that the operator at station number 16 wants thetransporter unit to come to his station. He would first glance at thepair of signal lights 48 and 49 which are part of his station circuit.If the transporter had not yet completed its previously programmed cycleof operation or if the transporter movement was already being programmedby another station, the red signal light 48 would be lit, thus informingthe operator at station 16 that the transporter was not yet availablefor a new program of movement. However, under the assumed conditions,where the cycle of operation of the transporter has been completed andthe transporter is available, the red signal 48 will not be lit butinstead the green signal light 49 will be lit to give visual indicationto the operator at station 16 that he can proceed with the programmingof the transporter.

It will be assumed that the dial type pulsing selector 45 has acapability of selectively providing from one to ten electrical pulsesthrough intermittently cammed contacts 50 in response to movement of theselector dial. The finger openings on the selector dial would thereforebe conventionally marked with numerals or numerical digits fromonethrough to indicate the number of pulses which will be produced by thecontacts 50 at each of the. 10 possible positions of rotation of thedial. Thetenth position is conventionallyin the numeral 0 rather than bythe numeral -will dial the number of his station on the selectormechanism byl'irst dialing the numeral or position 1 to cause thecontacts 50 to close once during the return spin of the dial which, aswill appear hereinafter, will cause a single electrical pulseto betransmitted to the control line 42. The movement of the selector dialcauses immediate closing of a second set of contacts 51 in the selectorunit and maintains these contacts in'a closed position during the timethat the selector dial is in motion and until it returns to its originalposition of rest. The closing of the contacts 51 complete an energizin gcircuit to the station relay 52 to cause the closing of its threenormally open contacts. The closing of contact 53 will energize stationrelay 54 by connecting it to the satellite hot line 36. This causes thenormally open contact of relay 54 to close and energize station relay55, thus serving to keep the connection of the contact 53 to satellitehot line 36 isolated from the hot line connections of the remainder ofthe circuit. The contact of relay 54 serves as part of the feeding linefor relay 55, thus preventing feedback to satellite line 36 through theholding contact 56 of relay 55 after it has been energized by theclosing of the normally open contact of relay 54. Once it has beenenergized, relay 55 will hold itself in an energized state through itscontact 56 and through the normally closed contact 57 of a ther mal timedelay element 58. Thus by spinning the dial selector to the digit 1 thecontacts 51 are closed to energize relay 52 which, in turn energizesrelay 54 by connecting it to the satellite hot line 36, and relay 54 inturn energizes relay 55 which has its own holding circuit so that, onceenergized, it stay energized independently of the de-energization of therelays 52 and 54 which occurs after the movement of the selector dialhas ceased. At the same time, the single intermittent closing of thecontacts 50 will transmit an electrical pulse from the hot line 34through the now-closed contact 59 of relay 52to the multi-pulse controlline 42 which communicates with the responding circuit. While the relay52 remains energized, its then closed contact 60 will connect the hotline 34 to the control line 43 to effectively produce a single pulse tothe line 43, which communicates with the responding circuit.

As soon as the spin of the dial is completed, the contacts 51 of theselector 45 open to tie-energize relay 52, causing its contacts to openand dc-energize the relay 54. However, through its own holding circuitof contact 56, the relay 55 remains energized and through its nowclosedcontact 61 connects the neutral power line 35 to the satellite powerline 37. When the line 37 thus becomes energized, it causes energimtionof the relay 47 which opens the contact 46 to disconnect the satellitepower line 36 from its connection to the hot line 34. When relay 47 isenergized, the normally open contact 62 is closed to energize a thermaltime delay element 63 which is designed to have a timeout after theresponding circuit is'fully programmed and the transporter is already inmotion, although it is energized and starts timing simultaneously withthe previously described time delay element 58, whose timing period ismerely sufficient to allow a reasonable time for the station selectionprocedure of dialing two digits. Energized relay 47 also causes theclosing of contact 64 which, through the normally closed contact 65 ofthe time delay 63 establishes a second feeding circuit for the satelliteneutral power line 37. Thus, the instant that relay 47 becomesenergizedthrough contact 61, the common satellite power line v36 becomesde-energized so that none of the other stations can initiate anyprogramming of the transporter unit in a similar manner as, in theabsence of power in the line 36, none of the other station relays 54 nor55 can be energized nor will there by any hot line connection to thecontacts 59 and 60 of the relays 52 in the other stations fortransmitting pulses to the control lines 42 and 43.

However, atstation 16, the holding circuit established by the contact 56for the relay 55 is still maintained through the contact 57 of the timedelay element 58 and maintains relay 55 energized and provides hot linepower to the contacts 59 and 60 of relay 52 when relay 52 is againenergized by the second spin of the dial of the selector 45 to the digitposition 6. The time delay device 58 is designed to have a sufficientduration, e.g., -15 seconds, to allow sufficient time for normalmanipulation of the selector dial twice, or through two dialing cycles.When the digit 6 is dialed, the selector contacts 51 again close toenergize relay 52 and close the relay contacts 53, 59 and 60. Theclosing of the contact 53 will, due to lack of power in the satellitepower line 36, have no effect upon station relay 54 and it will notbecome energized. Relay 55 will still remain energized as a result ofthe first spin of the selector dial so that the six intermittentclosings of the contacts 50 of the selector 45 will be transmitted assix electrical pulses from relay contact 59 to the control line 42.Similarly, the effective single electrical pulse established during theenergization of the relay 52 will be transmitted through the contact 60to the control line 43.

After the time delay of 10 or seconds for which it has been designed,the normally closed contact 57 of the time delay device will open andbreak the holding circuit through the contact 56 to causede-energization of the relay 55. The opening of the relay contact 61will break the neutral power feed established by this contact to thecontrol line 37, but the control line 37 will still remain energizedthrough the feed line established through the contact 65 of the timedelay element 63. When the element 63 times out, the contact 65 willopen to break the neutral power feed to the control line 37, therebymaking this line dead and causing the deenergization of the relay 47 torestore the common circuit to its original state or condition in whichthe normally closed contact 46 again feeds hot line power to thesatellite line 36. However, despite the establishment of thispre-existing condition, the responding circuit will not accept anyadditional pulse programming from any station in the system until theresponding circuit has been reset after completion by the transporter ofits previously programmed cycle.

The common circuit relay 66 is provided with a normally closed contact67which establishes an energization circuit for the green light 49 at allstations through the common control line 39. When the responding circuit30 has been energized by pulses from any station, it will causeenergization of the relay 66 through line 31, which will cause contact67 to be opened extinguishing the green light 49 and cause contact 68 ofrelay 66 to close to energize the circuit to the red signal light 48through the common control line 40. The red lamp will be lit at allstations to indicate-that the responding circuit will not accept anyprogramming. The red lamp 48 will remain lit at all stations until theresponding circuit is reset at the completion of the transporter cycle,at which time the line 31 becomes deenergized and relay contact 68 isopened while relay contact 67 is closed to again light the green lamp 49and extinguish the red lamp 48 at all stations.

The description of the material handling system now continues byreference to the responding circuit shown in FIG. 3 of the drawings.

In FIG. 3 of the drawings, the dotted line block indicated by thereference numeral 69 designates the starting circuit for the transporterI1 and the components which are physically mounted on the transporterunit. Another series of dotted outline blocks in FIG. 3 are designatedby the reference characters 16, 38 and to indicate that these componentsof the circuit are physically located at stations 16, 38 and 75respectively, although forming part of the responding circuit which isshown in the remainder of FIG. 3.

In order that the responding circuit 30 be receptive or set to receiveand react to the electrical pulse signals which are transmitted to it bythe selector dial at any one of the several stations, it is necessarythat a main responding relay 70 and a circuit holding relay 71 be in anenergized state. This can only be initiated by momentarily depressing aspring-loaded push-button switch 72 which is physically located in thestarting circuit of the transporter and will for convenience be referredto as the release" button.

When the release button 72 is momentarily depressed, it closes contact73 to feed power from the hot line 34 through the normally closedcontact 76 of relay 74 to the bus bar line 33. This hot line power fromthe line 33 is fed through the normally closed contact 78 of a relay 77to a release relay 79 for the purpose of energizing it momentarily whilethe release button remains depressed. The closing of the contact 80 ofenergized relay 79 feeds power from the hot line 34 to the relay 70 andalso to relay 71 to cause energization of both of these relays. Throughthe now closed contact 81 of the relay 71, a hot line circuit isestablished through the normally closed contact 83 of a time delay relay82, which serves as a holding circuit for the relays 70 and 71 andmaintains them energized after the release button is restored to itsoriginal position and the relay 79 is no longer energized. However,before being de-energized, the contact 84 of the relay 79 has beeneffective to transmit at least a momentary pulse of hot line power tothe normally open contact 86 of a flip flop relay and has similarly fedhot line power through contact 87 of relay 79, through lines 89 toenergize the reset devices 90 and 91 which are associated operativelywith stepping relays 92 and 93 respectively. Each of the stepping relayshas a movable contact arm 94 which is restored to its neutral ornoncontact position, shown in the drawing, by means of the reset devices90 and 91 so that any pulse-actuated movement of the contact arms 94will be initiated from the neutral position. It is also necessary thatthe pulseactuated flip flop relay 85 also have a uniformly consistentcontact position at the start of each operating cycle of the transporterunit. For that reason, the previously described hot line pulse isprovided to the contact 86 to momentarily energize the relay 85 andrestore its contacts to the position shown in the drawing in the eventthat they were not already in that position. Obviously, if the contactsof the relay 85 are already in the desired starting position shown onthe drawing, then the contact 86 will be open and there will be noefi'ect on relay 85 as a consequence of the hot line energization of thecontact 86 through contact 84 of relay 79.

In summary, by depressing the release button 72 on the transporter unit,the release relay 79 is momentarily energized. The contacts of therelease relay 79 serve to effect resetting action .of the contact arms94 to a neutral starting position on their respective relays; set

the flip flop relay to a consistent starting position of its contacts inthe event that it is not already in such a position; energize the mainresponding relay 70; and energize the holding relay 71 which establishesa holding circuit for itself and for relay 70 which is independent ofthe maintenance of energization of the relay 79 which is energized onlymomentarily by depression of the release button.

Through its now closed contact 95, the relay 70 establishes a circuitbetween the pulse control line 43 and one side of the flip flop relay85. Through its now closed contact 96, the relay 70 establishes acircuit between the pulse control line 42 and the setting or actuatingdevice 97 of the stepping relay 92 or, altematively to the setting oractuating device 98 of the stepping relay 93, depending upon whether theflip flop relay 85 is completing the circuit through its contact 99 orthrough its contact 100.

Through its connection by line 101 to the neutral line 35, the flip floprelay 85 is in readiness for energization by the hot power line pulsefrom line 43. The responding circuit 30 is now activated or set toreceive and react to the programmed selector pulses initiated at any oneof the stations in the system.

When the operator at station number 16 operated the selector mechanismto dial the digit 1 and then'dialed the digit 6 to call thetransporterto station number 16, two sets of electrical pulses weretransmitted to the responding circuit by the control lines 42 and 43. Assoon as movement of the selector mechanism 45 was initiated by theoperator, the contacts 51 closed to energize relay 52 which, through itscontact 60 connected the hot line 34 to the control line 43. Thisconnection is maintained both during the clockwise and counterclockwisemovement of the selector dial and results in a single power pulse whichchronologically precedes and then becomes contemporaneous with the pulseor pulses produced by the selector contacts 50 on the return spin of theselector dial and transmitted to the control line 42.

The single electrical pulse carried by the line 43 is transmittedthrough contact 95 of relay 70 in the responding circuit to the hot sideof relay 85 to energize the flip flop relay and cause its contacts 99and 86 to close and to maintain these contacts in this position untilthe control line 43 transmits another pulse to the hot side of the relay85.

On the return spin of the selector dial 45 from the digit position 1, asingle momentary electrical pulse is transmitted through control line 42and through contact 96 of relay 70 through the now closed contact 99 ofrelay 85 to the actuating or setting device 97 which is therebyenergized to cause movement of the contact arm 94 into engagement withelectrical contact 1 of stepping relay 92. Inasmuch as the contact arm94 of the stepping relay 92 is connected to the hot line 34, its comingto rest on contact 1 ofthe stepping relay 92 will complete a hot linecircuit from contact 1 to one side of the thermal time delay element 102and will energize a thermal time delay element 103. The time delayelement 102 will not yet be energized, as there is not yet any neutralpower feed to complete the energization circuit to this device.

After the completion of the first spin of the selector dial 45, theselector contacts 51 open and relay 52 is de-energized and its contact60 open to break the previously existing hot line connection to controlline 43. On the second spin of the selector dial to the digit position6, the selector contacts 51 again close and the control line 43 again isconnected to the hot line 34 and transmits a single pulse of power toagain energize the flip flop relay and cause reversal of its contacts,so that the contacts 99 and 86, which were previously closed, are openedand the previously open contact 100 is closed. The contact 100 performsthe same function for the stepping relay 93 as the closed contact 99performs for the stepping relay 92. On the return spin of the selectordial from its number 6 position, the selector contacts 50 are caused toclose and open six times and transmit six hot line electrical pulsesthrough control line 42 and through contact 96 of relay 70 and contact100 of flip flop relay 85 to the setting mechanism 98 of stepping relay93. The contact arm 94 of the relay 93 will advance by one step orcontact for each pulse that is received by the setting device 98. inresponse to the first pulse received from the line 42 by the actuatingmechanism 98, the contact arm 94 will move into contact with the contact1 of stepping relay 93. However, the contact arm 94 will not rest uponcontact 1 for a sufficiently long period of time to cause effectiveactuation of any of the thermal time delay devices that are connected ormight be connected to be fed by contact 1, as the next pulse transmittedby the control line 42 will advance the contact arm 94 to electricalcontact with contact 2 of stepping relay 93. Suecessive pulsestransmitted by the control line 42 will sequentially advance the contactarm 94 to contact 6 of the stepping relay where it will come to rest.Upon completion of this second spin of the selector dial, the selectorcontacts 51 will again open and, in the manner previously described, thecontrol line 43 will be deenergized and the hot line connection to theflip flop relay 85 will be broken.

The contact arm 94 of the stepping relay 93 is connected to the neutralpower line 35 and, by its connection with contact 6 feeds the neutral tothe other side of the thermal time delay 102 to energize it.

The thermal time delay unit 102 is unique to the station circuit ofstation 16. It will only be energized when station 16 is called for bythe selector mechanism. One such thermal time delay device, such as thedevice 104 for station 38 and the device 106 for station 75, must beprovided in the responding circuit for each active station in thesystem. By contrast, the thermal time delay device 103 is not unique toany individual station, but is only unique to the contact 1 on thestepping relay 92. One such thermal time delay device is provided in theresponding circuit for connection to each active contact of the steppingrelay 92. Thus in the illustrated embodiment, in addition to the timedelay 103, there is also provided a thermal time delay connected to theactive contact 3 of relay 92 and a thermal time delay device 107connected to the active contact 7 of this stepping relay. If every oneof the contacts of the relay 92 were an active or used contact, thenseven additional thermal time delay devices would be required in theresponding circuit for connection to these additional active contacts.Regardless of the number of two digit stations which are activelyutilized in the system, there would be a maximum quantity of ten of suchthermal time delay devices like 103, 105 and 107 which would berequired. Thus, if there were ten stations in the system identified bythe consecutive station numbers 10 through 19, the only active contactof the stepping relay 92 would be contact 1 and the previously describedtime delay devices 105 and 107 would not be needed. This is merely adramatization of the previously described assertion that one of thesethermal time delay devices is utilized for each active contact of thestepping relay 92 and that the number of these devices bears nonecessary relationship to the number of stations involved in the system,although it would have a relationship to the numbering system which isemployed for these stations. The group of time delay devices 102, 104and 106, as well as the group of time delay devices 103, 105 and 107,all have normally open contacts. One group of these time delay devices,such as the device 102, is only operatively effective when there isproper programming of the responding circuit, whereas the other group oftime delay devices, such as the device 103, is operatively effectivewhen there has been error or unreasonable delay in the programming. Thisdistinction is explained more fully hereinafter.

The time delay device 102 has a short delay on the order of 5 seconds orless, after which it causes its contact 108 to close to complete a hotline energizing circuit to the relay 109 which is identified withstation 16. After energization, the contact 110 of relay 109 willestablish a holding circuit for relay 109 through the normally closedlimit switch 111 which is physically located at station 16 and which isadapted to be opened by the trip arm 18 on the transporter 11 when itreaches its station of destination. Another contact 112 of the relay 109serves to energize the solenoid actuated trip arm 24 at station 16. Athird contact 113 on the relay 109 feeds hot line power from the line 34to the common line 31 which runs between the common circuit 29 and theresponding circuit 30, which power is transmitted through the now closedcontact 114 of the relay 71 to energize the time delay device 82 whosedelay may be on the order of 15 seconds or less and which may have asubstantially immediate reset capability after it has timed out. Whenthe device 82 times out, the normally closed contact 83 opens to breakthe holding circuits for the relays 70 and 71, wherebythe contact 114 ofrelay 71 opens to also break the energization circuit to the time delaydevice 82. The now open contacts 95 and 96 of the de-energized relay 70break the connection between the responding circuit and the pulsetransmitting lines 43 and 42 so that the responding circuit will beincapable of accepting any pulses which may thereafter be transmitted tothe lines 42 and 43 by any of the stations.

When the device 82 times out, its now closed contact 115 feeds hot linepower to energize a relay 116 to close its contacts 117 and 118 to resetthe stepping relays 92 and 93 through line 89 to the reset devices 90and 91, as well as to provide a resetting pulse to the flip flop relay85 to reverse its contacts to the desired uniform starting positionshown on the drawing, if they are not already in this position.

The now closed third contact 119 of the time delay device 82 provideshot line energization for the relay 77 to momentarily energize it andclose its normally open contact 120. The contact 120 will feed a hotlinepulse to the bus bar line 33 to energize the starting circuit 69 of thetransporter. As soon as the delay device 82 resets itself, the relay 77will become de-energized. Thus, in its de-energized state, the relay 77through its contacts 78 feeds hot line power from the bus bar 33 to therelease relay 79 in response to the momentary depression of the releasebutton 72; whereas in its energized state, the relay 77 through itscontact supplies hot line power to the bus bar 33 to provide thestarting pulse for the transporter.

Before describing the circuit components of the transporter startingcircuit 69, the additional time delay devices 121 and 122 which formpart of the responding circuit, will be described in relation to thesafeguards provided against delayed or erroneous dialing of the callingnumber of a station. One side of the thermal time delay device 121 isconnected to the neutral power line 35 and the other side is connectedto each unused or non-active contact of the stepping relay 92, thesebeing the contacts 2, 4, 5, 6, 8, 9 and 0 in the particular illustrationshown. Conversely, the thermal time delay device 122 has one sidethereof connected to the neutral power line 35 and has the other sidethereof connected to each unused or non-active contact of the steppingrelay 93, these being contact numbers 1, 2, 3, 4, 7, 9 and 0 in theillustration shown. Whenever the contact arm 94 of the stepping relay 92momentarily engages one of its inactive contacts, the delay device 121will be energized, but only momentarily and for a time which is notsufficient to cause closing of its normally open contact 123. Similarly,the momentary engagement of the contact arm 94 of stepping relay 93 withany of its unused contacts, will momentarily energize the delay device122, but not for a sufficient time to close its normally open contact124. It will be noted that both the contacts 123 and 124, when closed,will complete an energization circuit to the relay 116 which will causethe stepping relays 92 and 93 to be reset.

If through error, the selector dial at any station were dialed thenumber of the non-Oexistent station 28, the contact arm of the steppingrelay 92 would come to rest on its contact 2 and the contact arm of thestepping relay 93 would come to rest on its contact 8. With thiscombination of contacts on the stepping relays 92 and 93, none of thestation time delay devices 102, 104 or 106 would be energized, nor wouldany of the time delay devices 103,105 or 107 be energized, nor would thetime delay device 122 be energized. However, the time delay device 121would be energized and would, after a suitable delay of 15 to 30seconds, close its contact 123 to energize the relay 116 and reset thestepping relays 92 and 93 so that the responding circuit will be resetfor the call number of a properly dialed existing station. The samesequence of events would take place if the dialed station number had, asits first digit, a number represented by an inactive or unused contacton the stepping relay 92. The same sequence of events would occur withsuch an unused number, even if the second digit of the station numberwere not dialed at all.

If the non-existent station number being dialed is a number such as thenumber 11 for example, then the time delay device 121 would not beenergized because the contact 1 on the stepping relay 92 is not anunused or inactive contact and the device 121 is not connected to theused active contacts on the relay 92. However, the second digit of thisnon-existent station is represented by contact 1 on the relay 93 and,when the contact arm 94 comes to reset on this contact, it will energizethe time delay device 122 to close the normally open contact 124 andenergize the relay 116 to reset the stepping relays 92 and 93. This sameenergization of the time delay device 122 would occur whenever thecontact arm 94 of the stepping relay 93 comes to rest on an inactive orunused contact for a sufficiently long time to complete the closing ofthe contact 124 of the device 122. Thus, the two time delay devices 121and 122 will reset the responding circuit if either of the two digits ofthe call station number is represented by an unused or inactive contacton the stepping relays. Both the time delay devices 121 and 122 will beenergized if the erroneous station number is a number such as 21 inwhich both the first and second digits are represented by inactivecontacts on the stepping relays.

There is a third erroneous selector situation which may be exemplifiedby the non-existent station number 18. As the first digit of thisstation number is represented by a used or active contact on thestepping relay 92 and the second digit is represented by an activecontact on the stepping relay 93, neither the time delay device 121 nor122 would'be energized by this dialing sequence. Nor would thestation-identified time delay devices 102, 104 and 106 be energized bythese settings of the stepping relays 92 and 93. However, the time delaydevice 103 is energized when the contact arm 94 of the stepping relay 92comes to rest on the contact 1, regardless of whether the second digitof the station number is that of an existing station, such as thestation 16, or a non-existent station, such as the station 18. The timedelay devices 103, 105 and 107 which are connected to the activecontacts of the stepping relay 92, have the longest duration of delay ofany of the time delay devices utilized in the system. For example, thisgroup of time delay devices could have a delay duration of more than 60seconds, which would be a longer duration that that of the devices 121and 122, which in turn would have a longer duration that the time delaydevice 63 in the common circuit which in turn has alonger duration thaneither the device 58 in the station circuit or the time delay device 82in the responding circuit. i

When the time delay device 103 is energized for a sufficiently longperiod of time, its normally open contact 125 becomes closed to completean energization circuit to the resetting relay 116 which then resets theresponding circuit. Thus, whether the dialing of the selector isineffectual because only one digit of the two digit station number hasbeen dialed within a reasonable period of time, or because anon-existent station has been dialed, the resetting time delay devicesdescribed will be effective to reset the responding circuit and make itreceptive to proper dial selection, instead of permitting it to remainin an inoperative and nonresponsive status quo which could otherwiseonly be inconveniently remedied by locating the transporter unit anddepressing its release button to reset the responding circuit.

In response to the starting pulse received by the bus bar 33 from themomentary energization of therelay 77, an energization circuit for arelay 126 is established through the nonnally closed contact 127 of therelease button 72. The relay 126, through its now closed contact 128,establishes an energization circuit for the relay 74 and isolates thiscircuit from the bus bar 33 so that the bus bar need not be poweredduring the entire time that the relay is energized.

The now closed contact 129 of relay 74 establishes a holding circuit forthe relay 74 which is independent of the de-energization of the relay126 which results after the momentary pulse of power to the bus line 33has been completed. This holding line includes a normally closed contact130 of ganged limit switch 25, a normally closed contact 132 of anemergency stop button 131, and a normally closed contact 133 of therelease button 72.

The now closed contact 134 of the relay 74 feeds hot line power to thenormally closed contact 136 of a relay which establishes an energizationcircuit for a thermal time delay device 137 which has a normally opencontact 138. After the time delay device 137 times out, the contact 138will close to energize the relay 135 and break the 'energization circuitto the time delay device by opening the previously closed contact 136. Anow closed contact 139 of the relay 135 provides a holding circuit forthe relay 135 which is established through the normally closed contact140 of the emergency stop button 131 and through a normally closedcontact 141 of the ganged limit switch 25. These limit switch contacts130 and 141 are in series with the previously described holding circuitsof the relays 74 and 135 and the switch 25 is positioned to be trippedby an energized solenoid-operated trip at any one of the stationlocations, such as the trip 24 previously described with reference tostation 16.

A third contact 142 of the relay 135 serves to complete the circuit tothe transporter drive motor 143, either directly as shown oralternatively through any suitable motor starting devices known to theart. As a consequence, the transporter unit now initiates its movementon the track 12 and will continue such movement until its limit switch25 is engaged by the solenoid-energized trip 24 at station 16, which isthe selector dial station in the example herein described. When the trip24 opens the contacts 130 and 141, the holding circuit to the relays 74and 135 is opened and these relays are de-energized. The motor 143 isdeenergized andthe transporter unitcomes to a stop at the selectedstation.

Immediately following the engagement of the limit switch 25 by the trip24 to de-energize the motor 143, the trip arm 18 on the transporterengages the limit switch 11 l to break the holding circuit of the relay109 and cause it to be de-energized. The momentum of the transporter,even after its motor has been de-energized,

is sufficient to carry it the inch or two required for engagement withthe limit switch 1 1 1.

At this point, a conventional hoist mechanism carried by the transporterunit can be activated to either load or unload the material carried bythe hoist, or such other disposition may be made of the material atthestation 16 as is desired. As soon as the transporter unit has fulfilledthe purpose for which it was called to station 16, the operator atstation 16 depresses the release button 72 to activate the respondingcircuit in the manner previously described and make it receptive tostation selector dialing. If the operator at station 16 requires thatthe transporter be sent to another station, the operator at station 16can dial the number of that other station and start the transporter onits way, after the release button has been depressed. On the other hand,if the operator at station 16 has no reason to send the transporter unitto any other station, it will simply remain at station 16 until anyother station calls it. As previously described, during the time thatthe transporter was being programmed for station 16 and during itsmovement to and unloading at the station 16, the red signal lights 48 ateach station were lit to make the operators at all stations aware thatthe transporter was not available for programming at that time. Afterthe operator at station 16 depresses the release button, the red signallight 48 is extinguished and the green signal light 49 is lit, so thatall stations become aware that the transporter unit is available forprogramming and use.

By reference to FIG. 1 of the drawings, it will be noted that station 16is located on the main line of the track 12, so that the transporterunit 11 does not have to be switched over to any of the branch lines 12aor 12b in order to reach its programmed destination. If, instead ofutilizing the example of station 16 as the station of destination,station 38 were the station of destination, the selection procedure andcircuitry previously described would be employed in programming travelof the transporter unit to station 38.

However, inasmuch as the station 38 is located on the branch line 12a,its station circuit, through the contact 112 of the energized relay 109for station 38, would feed power to the normally open limit switch 15which, when closed, activates the rail switch 13 at the entrancejunction of the branch line 12a and the main track 12. When thetransporter unit 11 passes the limit switch 15 on the track 12, the trip18 on the transporter unit closes the limit switch 15 an causes thetrack switch 13 to be activated to direct the transporter unit onto thebranch line 12a.

As the transporter unit proceeds along the branch line 12a, its trip 18engages the always energized limit switch 17 to cause the rail switch 13to be returned to its original position. When the transporter arrives atthe location of station 38, the solenoid actuated trip 24 at station 38engages the ganged limit switch contacts 130 and 141 on the transporterto cause it to stop at the station.

Assuming that the release button on the transporter has been depressedto activate the responding circuit 30, if station 16 were to call thetransporter unit, the unit would proceed counter-clockwise from station38 on the branch track 12a to the main track 12 where it would continuein a counter-clockwise direction until it reached its destination atstation 16. This is based upon the exemplary endless track arrangementshown in FIG. 1 of the drawings. Of course, if a non-endless track wereused, the programming would direct the transporter unit in one directionor the other on the non-endless track depending upon the direction ofthe station to which the transporter unit-is sent in relation to itsthen location.

By way of further example, in the form of arrangement shown in FIG. 1 ofthe drawings, if station 75 were the calling station, the contact 112 ofits energized relay 109 would not only close a circuit to the limitswitch 15 through line 23 but would also close a circuit to the limitswitch 19 through the line 21. Therefore, wherever the transport unitwas then located, after it had been guided onto the branch track 12a byclosing of the limit switch 15 by engagement with the trip 18, it wouldthen close the limit switch 19 to energize the track switch 14 whichwould direct the transport unit onto the branch track 12b and to thestation while activating the track switch return limit switch 20 duringthe course of its movement. Thus, in addition to utilizing the contact112 of the station identified relay 109 to energize thesolenoid-actuated trip 24, this contact is also utilized to feed powerto any and all of the limit switches which energize the track switcheswhich lie in the path of movement of the transporter unit to theselected station. Although the main track and its branches 12a and 12bcould all be on the same level, it is also possible, for example, thatthe main track 12 be at one level and that the branch tracks 12a and 12bbe at a higher or lower level so as to permit material to be moved bythe transporter unit from one level to another in response to theprogramming of the system.

In the event there is any need or reason to stop the movement of thetransporter 11 before its cycle of operation has been completed, theemergency stop button 131 can be depressed to de-energize the startingcircuit 69 and make the entire system inoperative until the releasebutton 72 on the transporter unit is again depressed.

With the illustrative arrangement herein described, a total of stationscould be utilized, using two digit numbers for identification of all ofthese stations. As previously mentioned, the addition of a station onlyrequires that the circuit components of the new station be connectedinto the existing control lines which are common to all the stations. Inthe responding circuit, it is necessary to add a time delay device andrelay identified to the new station.

In lieu of utilizing the described form of flip flop relay to direct thestation selector pulses alternately to the stepping relays 92 and 93, astepping relay could be utilized for this purpose. By replacing the flipflop relay with a stepping relay, additional responding relays, such as92 and 93 could be employed in the system with the station selectorpulses directed sequentially to these responding relays. For example, ifthree such responding relays were utilized, a three digit stationidentification system would be used and the system would have acapability of 1,000 stations.

Although the system and its circuitry have been described in relation tothe operation of a material handling transporter, it will be apparentthat the system circuitry could be utilized without the transporter forapplications which require only selective station activation toaccomplish some desired remote control function at the selected station.For example, an activated station could be used to switch certain othercontrol or operating circuits in a pre-determined arrangement, or anactivated station could control a hopper, discharge chute, door orsimilar dispensing or ejecting device for discharging material onto aconveyor or the like in a warehousing or processing operation or even inan automated restaurant operation. In some of such applications, thedial selector would only be provided at one central station, in otherapplications the dial selector might be provided at only some of thestations, but not at all of them.

It is to be understood that the forms of my invention herein shown anddescribed, are to be taken as preferred examples of the same, and thatvarious changes in the shape, size and arrangement of parts may beresorted to, without departing from the spirit of my invention, or thescope of the subjoined claims.

Having thus described my invention, I claim:

1. In a material handling system having a track, a track-mountedpower-driven load-carrying transporter, and a plurality of work stationslocated adjacent to the track, the combination of an electricalstation-operating circuit for each station, a common electrical controlcircuit inter-connecting all stations, a dial-operated selectiveelectrical pulsing station selector included in said station circuit andadapted to provide station identifying pulses, an electrical respondingcircuit connected to said common circuit and to the starting circuit ofsaid transporter, circuit components in said responding circuit forenergizing a selected station circuit in response to electrical pulsetransmissions from a station selector at any station, means in saidresponding circuit for initiating power-driven movement of saidtransporter toward a selected station in response to energization ofsaid selected station circuit, and means for opening the driving circuitto said transporter in response to arrival at said selected station ofdestination.

2. A combination as defined in claim 1, including a power line, asatellite power line in the common circuit connected to said power linefor energizing all the station circuits, and means in the commoncircuit, responsive to actuation of a station selector at any one of thestations, for disconnecting said satellite line from all the stationcircuits and connecting said power line directly to said selectingstation circuit, whereby only said actuated station selector isoperative to transmit electrical pulses to said common circuit.

3. A combination as defined in claim 1, wherein said station selectortransmits a single signal pulse during its actuation and separatelytransmits one or more intermittent station-selection pulses during suchactuation, and including a single-pulse transmission line in said commoncircuit and connected to said responding circuit, a multi-pulsetransmission line in said common circuit and connected to saidresponding circuit, a first stepping relay and a second stepping relayin said responding circuit, means responsive to transmission of a firstsignal pulse for directing pulses from said multi- 7 stepping relay,whereby each group of selection pulses resulting from actuation of saidstation selector is directed to a different stepping relay to efiectdigital positioning thereof for electrical contact.

4. A combination as defined in claim 1, including electrically operatedtrack switches for selectively directing transporter movement ontodifferent sections of track, means in the station circuit forestablishing an energizing circuit to controls for selected trackswitches, and a single control-engaging element provided on said transrter for actuating each of said energized track swi ch controls mresponse to movement of said transporter past said controls, wherebysaid selected track switches are energized to direct said transporteronto. sections of track leading to the selected station of destination.

5. A combination as defined in claim 1, wherein said lastnamed meanscomprises a normally closed limit switch carried by said transporter inits driving circuit, and an electrically energized trip arm in thestation circuit at the station of destination disposed in the path ofmovement of said transporter limit switch, whereby to open said drivingcircuit.

6. A combination as defined in claim 3, including means in saidresponding circuit for disconnecting itself from said pulse transmissionlines in response to initiation of transporter movement, whereby saidresponding circuit is not receptive to pulse transmissions duringtransporter movement.

7. A combination as defined in claim 3, including a plurality of timedelay elements in said responding circuit, each adapted to complete aresetting circuit to said stepping relays after timing out.

8. A combination as defined in. claim 7, wherein said time delayelements have a progressively increasing duration of timing-out.

9. A combination as defined in claim 8, wherein the time delay elementsof longer duration are operative only upon failure of operation of thetime delay elements of shorter duration.

10. A combination as defined in claim 9, wherein the time delay elementsof shorter duration are operative solely in response to programmedstation selection pulses and the time delay elements of longer durationare operative in response to improper non-programmed station selectionpulses.

1 l. A combination as defined in claim .10, wherein a separate timedelay circuit-closing element of shorter duration is provided forselective energization of each station circuit, each of said separatetime delay elements being energized solely in response to a circuitestablished by a predetermined combination of electrical contacts closedby the stepping relays.

1. In a material handling system having a track, a track-mountedpower-driven load-carrying transporter, and a plurality of work stationslocated adjacent to the track, the combination of an electricalstation-operating circuit for each station, a common electrical controlcircuit inter-connecting all stations, a dialoperated selectiveelectrical pulsing station selector included in said station circuit andadapted to provide station identifying pulses, an electrical respondingcircuit connected to said common circuit and to the starting circuit ofsaid transporter, circuit components in said responding circuit forenergizing a selected station circuit in response to electrical pulsetransmissions from a station selector at any station, means in saidresponding circuit for initiating power-driven movement of saidtransporter toward a selected station in response to energization ofsaid selected station circuit, and means for opening the driving circuitto said transporter in response to arrival at said selected station ofdestination.
 2. A combination as defined in claim 1, including a powerline, a satellite power line in the common circuit connected to saidpower line for energizing all the station circuits, and means in thecommon circuit, responsive to actuation of a station selector at any oneof the stations, for disconnecting said satellite line from all thestation circuits and connecting said power line directly to saidselecting station circuit, whereby only said actuated station selectoris operative to transmit electrical pulses to said common circuit.
 3. Acombination as defined in claim 1, wherein said station selectortransmits a single signal pulse during its actuation and separatelytransmits one or more intermittent station-selection pulses during suchactuation, and including a single-pulse transmission line in said commoncircuit and connected to said responding circuit, a multi-pulsetransmission line in said common circuit and connected to saidresponding circuit, a first stepping relay and a second stepping relayin said responding circuit, means responsive to transmission of a firstsignal pulse for directing pulses from said multi-pulse transmissionline to said first stepping relay and responsive to a second signalpulse for directing pulses from said multi-pulse transmission line tosaid second stepping relay, whereby each group of selection pulsesresulting from actuation of said station selector is directed to adifferent stepping relay to effect digital positioning thereof forelectrical contact.
 4. A combination as defined in claim 1, includingelectrically operated track switches for selectively directingtransporter movement onto different sections of track, means in thestation circuit for establishing an energizing circuit to controls forselected track switches, and a single control-engaging element providedon said transporter for actuating each of said energized track switchcontrols in response to movement of said transporter past said controls,whereby said selected track switches are energized to direct saidtransporter onto sections of track leading to the selected station ofdestination.
 5. A combination as defined in claim 1, wherein saidlast-named means comprises a normally closed limit switch carried bysaid transporter in its driving circuit, and an electrically energizedtrip arm in the station circuit at the station of destination disposedin the path of movement of said transporter limit switch, whereby toopen said driving circuit.
 6. A combination as defined in cLaim 3,including means in said responding circuit for disconnecting itself fromsaid pulse transmission lines in response to initiation of transportermovement, whereby said responding circuit is not receptive to pulsetransmissions during transporter movement.
 7. A combination as definedin claim 3, including a plurality of time delay elements in saidresponding circuit, each adapted to complete a resetting circuit to saidstepping relays after timing out.
 8. A combination as defined in claim7, wherein said time delay elements have a progressively increasingduration of timing-out.
 9. A combination as defined in claim 8, whereinthe time delay elements of longer duration are operative only uponfailure of operation of the time delay elements of shorter duration. 10.A combination as defined in claim 9, wherein the time delay elements ofshorter duration are operative solely in response to programmed stationselection pulses and the time delay elements of longer duration areoperative in response to improper non-programmed station selectionpulses.
 11. A combination as defined in claim 10, wherein a separatetime delay circuit-closing element of shorter duration is provided forselective energization of each station circuit, each of said separatetime delay elements being energized solely in response to a circuitestablished by a predetermined combination of electrical contacts closedby the stepping relays.